Vacuum brazed or soldered assemblies offer superior advantages to conventional brazing or soldering, such as: flux-free joints, high strength and integrity of the joint, and the ability to heat-treat or age-harden the assemblies while simultaneously performing the joining process. Excess flux may cause corrosion over time, so a process that offers flux-free joining has an advantage in that there is no flux to remove after joining. However, vacuum brazing or soldering may be expensive due to the process being performed inside of a vacuum chamber vessel. In addition, vacuum brazed or soldered assemblies face a unique challenge of disassembly when retrofitting or repair is necessary.
The American Welding Society defines brazing as a joining process wherein a non-ferrous joining material or alloy is heated to a melting temperature above 842° F. (450° C.) and distributed between two or more close-fitting parts by capillary action. The joining material and a flux interact with a thin layer of the base material. When cooled, the joint is especially strong due to grain structure interaction. The American Welding Society defines soldering as a process whereby two or more metal components are joined together by melting and flowing a filler metal into the joint, the filler material having a melting point lower than a brazing material.
High temperature assemblies that are joined through vacuum brazing are especially difficult to disassemble for repair or retrofit. A vacuum brazed assembly is difficult to disassemble because introducing mechanical loading through the vacuum chamber walls to pull the pieces apart is problematic. Alternatively, such assemblies might be loaded by weights within the chamber and rely on gravity to disengage elements. The design of the assembly may require lateral loading to disengage. Loading by lateral cables and pulleys in a high temperature vacuum environment is extremely complex and difficult.